1. Field of the Invention
This invention relates generally to exercise machines, and is particularly concerned with an exercise machine for performing triceps dip exercises which has a moving user support.
2. Related Art
Free bar triceps dip exercises are typically performed by a user gripping two parallel bars, and lifting themselves from a position in which their elbows are bent with their hands just above their waist, and their body in a forward lean, into a position in which their arms extend straight down the side centerline of their body. The starting forward lean is a natural balancing by-product of a suspended exerciser performing a free bar triceps dip or bar dip exercise. The dip movement is one of the most fundamental exercises, and is performed by professional gymnasts, fitness training enthusiasts, as well as children in school yards. It is one of the standard measures of strength and fitness endurance. However, it can be difficult to many people to perform, requiring balance and coordination as well as strength for someone to raise and lower their body while trying to balance themselves with their hands. This exercise involves a compound or multi-joint movement that involves the shoulder, triceps, and chest muscles. Improper form by the exerciser, for example swinging, leaning too far forward, or arching backward, can make the exercise more difficult, increasing stress to the joints and potentially leading to injury.
The counter-balanced dip machine was developed to help less conditioned exercisers perform dip exercises and to provide a safer exercise. Some prior art triceps dip exercise machines have a fixed user support and a pivoting exercise arm linked to a suitable resistance. This results in an exaggerated and unnatural arcing movement which does not accurately duplicate a free bar dip exercise. Some examples of prior art exercise machines for performing both chin-up and dip exercises which have moving user supports are U.S. Pat. No. 3,707,285 of Martin, U.S. Pat. No. 5,011,139 of Towley, U.S. Pat. No. 5,322,489 of Webb, U.S. Pat. No. 5,449,959 of Holmes, and U.S. Pat. No. 5,540,639 of Potts. All of these machines use a load to counterbalance the user's body weight and assist them in performing the exercise, and have exercise arms which are stationary and fixed to the main frame. In Holmes and Webb, the user kneels on the user support, while the user is in a standing position on the support in Martin, Potts, and Towley. In order to perform a dip exercise, the user pushes on the exercise arm handles. While the user support moves in these designs, it is not urged to do so by movement of the exercise arm. The machines are quite large and awkward to use, requiring the user to climb up steps to mount the machines and step blindly backwards onto the steps in order to step off the machine. The starting user hand gripping position for the dip exercise in these machines places the wrists at an uncomfortable and unnatural angle which could lead to injury.
U.S. Pat. No. 5,876,095 of Johnston describes an exercise machine for performing a seated dip exercise. A user support seat is raised when handles are pushed downward. Both the se at and the handles travel in a linear and vertical direction on wheels or rollers mounted on a main frame. The seat is connected to the handles via a tether such as a cable or belt. This-machine also places the user's wrist in an awkward starting position, and relies on the user's body weight to provide exercise resistance, with no provision for adding further resistance.
The triceps press machines described in U.S. Pat. No. 5,421,796 of Jones and U.S. Pat. No. 5,803,882 of Habing work the triceps muscles, but do not involve the pectoral/chest muscles the way a dip exercise does. In both cases, the user support is in a fixed position during the exercise and pivotal movement of an exercise arm is resisted by an exercise resistance, such as a weight stack or the like. These machines do not keep the exerciser's arms aligned with the centerline of their body, which is their natural center of gravity. In Habing, the starting position places the exerciser's hands far in front of their body and forces them to go through a large arc, finishing with the arms positioned past the exerciser's body centerline.
Some known multi-purpose exercise machines for performing various different types of exercise have movable seats or user supports. In U.S. Pat. No. 5,330,405 of Habing, the machine has a stationary base frame, a lever arm pivotally mounted on the frame, and a sub frame pivotally connected to the base frame and supported by the lever arm. The sub frame comprises a user support and an exercise arm linked to the lever arm by cables and pulleys. The exercise arm is pivotally connected to a portion of the sub frame at a location above the user. In order to perform a shoulder press, the user must sit on the user support leaning forward at an angle without benefit of back support, pressing the exercise arm forward and rotating it about its pivotal connection to the sub frame in order to pull the cables and cause the sub frame to lift.
U.S. Pat. No. 5,669,865 of Gordon describes a multi-purpose exercise machine with a hinged, two-piece user support that folds and unfolds with each exercise repetition. The user support comprises a seat portion and a back portion which are pivotally connected together, and is pivotally connected to the main frame. A first exercise arm pivoted to the frame provides pressing and pull down exercises. The seat and back rest do not travel in a fixed relationship to each other, but fold and unfold during the exercise, working the abdominal and low back muscles even when other exercises are being performed. Due to the separate motion of the seat and back rest, additional supports such as a foot rest, safety belts, and thigh gripping surfaces are required to keep the user properly and safely-positioned. In this machine, most of the combined weight of the user and user support remains on one side of the gravitational centerline of the user support, and this weight is used as a partial exercise resistance. Due to the working of the abdominal and low back muscles in every exercise movement, including press exercises, the exerciser cannot properly isolate any one specific muscle or muscle group. Because of this, the exerciser cannot fully fatigue other muscles, since the abdominal and lower back muscles will always fatigue first.